patch 9.0.0338: return value of list_append_list() not always checked

Problem:    Return value of list_append_list() not always checked.
Solution:   Check return value and handle failure.
diff --git a/src/version.c b/src/version.c
index 1ff36ff..8091488 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    338,
+/**/
     337,
 /**/
     336,